When users log into a site (e.g. employing an authenticated unique identifier such as a username), it is easy to track respective users from multiple devices, browsers, applications, etc., in order to obtain count of unique users visiting the site. On the other hand, if a user is not logged-in to a site, an unauthenticated unique identifier, such as a cookie (e.g., small piece of data sent from a website and stored in a user's web browser), can be used as a surrogate to keep track of and count users. However, simply counting number of distinct cookies can greatly over or under count actual number of unique users. For example, a cookie can expire or a user can choose to delete the cookie, resulting in another cookie being generated. In another example, a user can block cookies completely such that no cookie will be generated for the user. In a further example, different devices, browsers, and/or applications can have different cookies resulting in multiple cookies being generated for the same user. Consequently, count of unique users associated with unauthenticated unique identifiers can be over or under counted.